coalaJSONTest: Add output file overwriting test
coalaJSONTest: Add output file overwriting test


Test if using `--output` overwrites files instead
of appending

Closes https://github.com/coala/coala/issues/4810
coala/coala,nemaniarjun/coala,coala-analyzer/coala,coala/coala,karansingh1559/coala,aptrishu/coala,karansingh1559/coala,SanketDG/coala,CruiseDevice/coala,coala-analyzer/coala,CruiseDevice/coala,aptrishu/coala,karansingh1559/coala,coala/coala,nemaniarjun/coala,coala-analyzer/coala,SanketDG/coala,jayvdb/coala,nemaniarjun/coala,Nosferatul/coala,shreyans800755/coala,jayvdb/coala,Nosferatul/coala,jayvdb/coala,aptrishu/coala,SanketDG/coala,Nosferatul/coala,CruiseDevice/coala,shreyans800755/coala,shreyans800755/coala